The ferroelectricity in ultrathin HfO2 offers a viable alternative to ferroelectric memory. A reliable switching behavior is required for commercial applications; however, many intriguing features of this material have not been resolved. Herein, we report an increase in the remnant polarization after electric field cycling, known as the “wake-up” effect, in terms of the change in the polarization-switching dynamics of a Si-doped HfO2 thin film. Compared with a pristine specimen, the Si-doped HfO2 thin film exhibited a partial increase in polarization after a finite number of ferroelectric switching behaviors. The polarization-switching behavior was analyzed using the nucleation-limited switching model characterized by a Lorentzian distribution of logarithmic domain-switching times. The polarization switching was simulated using the Monte Carlo method with respect to the effect of defects. Comparing the experimental results with the simulations revealed that the wake-up effect in the HfO2 thin film is accompanied by the suppression of disorder.

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The phase transition through local strain engineering is an exciting avenue for controlling electronic, magnetic properties and catalyst activity of materials but complex phenomenon in nanoscience. Herein, we demonstrate the first combinations of bending strain and 2H/1T phase transition by rolling up MoS sheets for improving catalytic activity in relatively inert basal plane surfaces and promoting electron transfer from the less-conducting 2H MoS sheets to the electrodes. Furthermore, we generate various MoS@Pt nanoparticle hybrids nanomaterials and especially MoS@Pt scrolls containing the coverage of Pt NPs (8.3 wt%) have a high catalytic activity (39 mV per decade). The rolled up MoS@Pt sheets with bending strain (2.4%) provide an intra-layer plane gliding that allows the transversal displacement of an S plane from the 2H to the 1T phases (28%). This unique combination also allows us to maximize the intrinsic HER activity among molybdenum-sulfide based catalysts.

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Bio-based polycarbonates containing cyclic ketal moieties were designed, and the bio-based diol monomer was synthesized by CQ with glycerol to improve their thermal properties and replace BPA in polymer industry. The molecular structure of the novel bio-based diol monomer 2,2:3,3-bis(4′-hydroxymethylethylenedioxy)-1,7,7-trimethylbicyclo[2.2.1]heptane (abbreviated as CaG) was analyzed by 1 H, 13 C, and 2D-COSY NMR techniques. GPC results show that CaG was reacted successfully and led to the high molecular weights for homopolycarbonate (M w = 18 652) abbreviated as PCaGC and for copolycarbonate (M w = 78 482) as PCaG 20 BPA 80 C. The high thermal stability (T d value above 350°C) and glass transition temperature (T g value from 128 to 151°C) of PCaGCs and PCaG x BPA y Cs were studied by TGA and DSC, respectively. Given the sufficient reactivity and high thermal stability, CaG is a promising renewable building block for applicable polymers.

Controlling phase transitions through local strain engineering is an exciting avenue for tailoring the electronic and magnetic properties of materials at the nanoscale. Herein, we demonstrate a tunable semiconducting to metallic phase transition of two-dimensional transition metal dichalcogenides using strain engineering through rolled up MoS sheets (named as MoS scrolls). A phase incorporated structure for MoS nanoscrolls containing the maximum concentration of 1T phase (∼58%) with high thermal stability up to 473 K can be produced by a gliding-rolling process for the S plane. These phase transitions are irreversible by virtue of the van der Waals interaction between the layers of the nanoscrolls, which is relatively stronger than the bending strain. A high concentration of the 1T phase can tune the bandgap through temperature, and also the magnetic property from nonmagnetic to paramagnetic MoS. This study, which is able to control phase transitions by strain engineering in the field of 2D materials, proves an exciting avenue for tailoring the novel functional properties of low-dimensional materials.

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